Warfarin pharmacogenetics

Pharmacotherapy. 2008 Sep;28(9):1084-97. doi: 10.1592/phco.28.9.1084.


Significant interest in the pharmacogenetics of warfarin therapy has been triggered with the recent package insert update that highlights the potential role of pharmacogenetics in improving the safety and effectiveness of warfarin. We review the evidence of the influence of the two key genes of interest, the cytochrome P450 2C9 gene, CYP2C9, and the vitamin K epoxide reductase complex 1 gene, VKORC1, on warfarin response and discuss the implications of current knowledge for clinical practice. The influence of CYP2C9 and VKORC1 genotypes on warfarin dose requirements has been consistently demonstrated in diverse racial and ethnic patient groups in observational studies and randomized clinical trials. Dosing algorithms have been developed that incorporate clinical, demographic, and genetic information to help select a warfarin starting dose. Furthermore, CYP2C9 variant genotypes have been associated with a significantly increased risk of serious bleeding events. However, evidence to date from prospective, controlled studies has not demonstrated an added benefit of incorporating genotype-guided therapy in improving anticoagulation control or in preventing or reducing the risk of hemorrhagic or thromboembolic complications. Research efforts designed to evaluate the effectiveness of genotype-guided therapy in improving outcomes are under way. However, the routine use of CYP2C9 and VKORC1 genotyping in the general patient population who begin warfarin therapy is not supported by evidence currently available.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Animals
  • Anticoagulants / administration & dosage
  • Anticoagulants / adverse effects
  • Anticoagulants / pharmacokinetics*
  • Anticoagulants / pharmacology*
  • Aryl Hydrocarbon Hydroxylases / genetics
  • Aryl Hydrocarbon Hydroxylases / metabolism
  • Blood Coagulation / drug effects
  • Cytochrome P-450 CYP2C9
  • Dose-Response Relationship, Drug
  • Hemorrhage / blood
  • Hemorrhage / chemically induced
  • Humans
  • Mixed Function Oxygenases / genetics
  • Mixed Function Oxygenases / metabolism
  • Pharmacogenetics*
  • Randomized Controlled Trials as Topic
  • Vitamin K Epoxide Reductases
  • Warfarin / administration & dosage
  • Warfarin / adverse effects
  • Warfarin / pharmacokinetics*
  • Warfarin / pharmacology*


  • Anticoagulants
  • Warfarin
  • Mixed Function Oxygenases
  • CYP2C9 protein, human
  • Cytochrome P-450 CYP2C9
  • Aryl Hydrocarbon Hydroxylases
  • VKORC1 protein, human
  • Vitamin K Epoxide Reductases